Current semiconductor manufacturing methodology requires "clean" processing environments that are relatively free of particle contamination. Generally, all semiconductor manufacturing steps are performed in a clean room in which the air is continuously filtered to remove particles. Unwanted particles introduced onto wafers can cause improperly defined features, undesirable surface topography, leakage through various insulating layers and other problems affecting circuit reliability. In a worst case scenario, particles introduced into the manufacturing environment can result in an unusable product causing the loss of considerable manufacturing time and costs.
During certain steps in the manufacturing process, the elimination of particles is more critical to producing a reliable product. For example, eliminating particles during chemical vapor deposition (CVD) process steps is critical to producing a reliable product. CVD equipment typically includes a loadlock chamber for loading wafers to be processed.
The loadlock chamber is connected to a process chamber where various chemical films are deposited onto the surface of the wafers. If the number of particles introduced into the process at this step is too high, the wafers may be rendered unusable.
Extreme care is typically taken to avoid the introduction of contaminants into the CVD process chamber. For example, complex cleaning routines, such as those disclosed in U.S. Pat. No. 5,607,515, are conventionally used to ensure that the number of particles in the process chamber are kept to a minimum.
A drawback with these conventional cleaning procedures is that they are time consuming and costly in a manufacturing environment. Another drawback with such procedures is that only the process chamber is cleaned, with no attention given to the loadlock chamber.
More particularly, conventional CVD loadlock chambers often include a cooling station for cooling the wafers after the chemical deposition in the process chamber. The cooling station typically contains areas that are relatively inaccessible to the human hand.
The loadlock chamber is not typically considered a major source of contaminants because it is not directly involved in the chemical deposition. In addition, the inaccessible parts of the equipment are generally not cleaned due to the belief that these parts are relatively immune from outside contamination. Therefore, the inaccessible parts of the loadlock cooling station are not cleaned to the degree required to reduce particles.